Blunder

Because ...Qf3 is mate next move. And if white tries to block it with either the knight or rook that piece drops.
Posting the game so people can see it rather than looking it up would be ideal. I just copy the PGN and when I insert a chess game I paste the PGN into it and hit flip board under theme since you are playing black this game. Comments after the moves and variations shown for extra effect.